No doubt, there is a 1000 variables. Each fish is an individual and every circumstance/situation is at least a little bit different.
But I have read a lot on forums for the last 10 years. Many people have tried salvini, and often as your suggesting. I have yet to find one thread that shows long term success with this set up.
From my own perspective, I am not real keen on just a pair of CA cichlids in a tank with out other cichlid tank mates.....but I don't rule it out as an option in a tank that incorporates a good divider. My own experience with many CA pairs that have gotten along fine in a community tank....... sometimes about 20 minutes by themselves in a tank is about all the time I need to Know there is no way there going to get along in that situation!
I don't buy the notion of ''well bonded pair". Some individuals will get along much better then others, but things can change on a dime, and a large male is capable of killing in a matter of minutes to hours. In nature there is a breeding season. Once fry are let go, they go there separate ways. It's an adaptation to captivity. Stuck in one place and abundance of calories keeping the female ready to lay frequently. But it is often the threat of other cichlids that keeps the pair together claiming a territory between spawns. Or at least the distaraction and diversion of other tank mates keeping the male form focusing too much on the female.
Just curious how many times and for how many years?
If they can swallow giant danios, they can just as easily swallow BA tetras. I'm not saying that happens every time, only that there is a definite risk. Of course the sals have to be large enough and it's certainly riskier when they are still rapidly growing. Older sals , IME, are often too lazy though there is still risk.
Seen a few threads where the aquarist went through a lot of dithers (all kinds including BA's and GD's), as young breeding sals would kill them fairly quickly after fry became free swimming.